The inventive concept relates to semiconductor devices, and more particularly, to semiconductor memory devices and to memory systems that include these semiconductor memory devices.
Semiconductor memory devices are used as storage devices in many, if not most, electronic systems. Dynamic random access memory (DRAM) devices refer to one particular class of semiconductor memory device that has been widely used to implement the memory systems that are used in, for example, personal computers and servers. A variety of different types of DRAM devices are known in the art including, for example, synchronous dynamic random access memory devices (SDRAM) which operate in synchronization with a system clock signal. One example of an SDRAM device is the double-date-rate (DDR) SDRAM, which delivers data in synchronization with rising and falling edges of a system clock signal. Numerous other semiconductor memory systems are known in the art including a wide variety of non-volatile memory devices such as, for example, flash memory devices, phase change memory devices, resistance memory devices and the like.